This study will be one of the first attempts to link the increased levels of estradiol and androgens/decreased levels of progesterone with miscarriages seen in women with PCOS to a mechanism which focuses on aberrant glucose utilization. Understanding the hormonal regulation of glucose uptake and metabolism in the uterine stroma during decidualization will potentially progress into the development of novel pharmacologic interventions to increase the rate of successful pregnancies in this population of women. This proposal is organized into three specific aims. In Aim 1, we will investigate the effects of high levels of estradiol/androgens and low levels of progesterone on expression of glucose transporters, glucose utilization and decidualization in murine endometrial stromal cells. We will also perform the same studies in human endometrial stromal cells. We hypothesize that high E2 and low P4 will downregulate GLUT1 and glucose uptake in mESCs and hESCs. In Aim 2, we will analyze the effects of changing GLUT1 expression as well as altering glucose metabolism on the process of decidualization of these cells. We will use siRNA/shRNA lentivirus to knockdown GLUT1, glucose flux studies to assess glucose utilization in these cells and then inhibit these pathways and assess decidualization in ESCs. We hypothesize that glucose is primarily metabolized via the pentose phosphate pathway during decidualization; and that inhibition either upstream (GLUT1 expression) or downstream (PPP inhibition) adversely affects decidualization. We will test this hypothesis in mouse and human ESCs. Finally, in Aim 3 we will focus on analyzing the in vivo effects of excess estradiol/androgen on decidualization and glucose utilization in the endometrial stroma by using a mouse model of increased DHEA. We will attempt to correct these effects by exposure to PPP activators used both in vivo and in vitro. We will also use leftover samples from patients with PCOS or oocyte donor patients and examine human ESCs. We predict that 1) DHEA exposed mice will have abnormal glucose utilization and thus abnormal decidualization with decreased numbers of pups, 2) the agents used to increase glucose utilization via the PPP will reverse decidualization abnormalities, and 3) human ESCs from these populations of patients will have similar abnormalities in glucose utilization.